1. Field of Invention
The invention relates to a condenser microphone and a manufacturing method thereof and, in particular, to a condenser microphone and a manufacturing method thereof wherein a plurality of protrusions are disposed on a diaphragm.
2. Related Art
The microphone is a kind of electronic component capable of converting acoustic signals to electric signals for transmission, belonging to a kind of electro-acoustic transducer. Based on different principles of the electro-acoustic conversion, the microphone is mainly divided into a moving coil type, a condenser type and a piezoelectric type. Among them, the condenser microphone has higher sensitivity, signal-to-noise ratio, lower distortion and better converting efficiency, so it becomes the mainstream of the microphone.
FIG. 1 is a schematic diagram of a conventional condenser microphone. In FIG. 1, the condenser microphone 1 includes a diaphragm 11, a back plate 12 and a substrate 13. The diaphragm 11 is disposed opposite to the back plate 12. The back plate 12 is disposed to the substrate 13 and has a plurality of holes 121. Without coil and magnet, the condenser microphone functions via changing the interval distance between the diaphragm 11 and the back plate 12, and the change of interval causes the capacitance variation that leads to a signal. When a sound wave enters into the condenser microphone 1, the diaphragm 11 is caused to vibrate, so that the interval between the diaphragm 11 and the back plate 12 is changed while the back plate 12 is fixed.
According to the capacitance characteristic, when the interval d between the diaphragm 11 and the back plate 12 is changed, the capacitance value is changed accordingly, and the capacitance value is inversely proportional to the interval d. The interval d is varied according to various oscillation frequencies. On the other hand, the sensitivity of the condenser microphone 1 will show nonlinearity under different acoustic pressures and frequencies, and this nonlinearity results in the distortion of the corresponding acoustic signals. Besides, if the back plate 12 is manufactured firstly, the surface (not shown) will become uneven easily, and therefore, the characteristic of the diaphragm that is made subsequently will not be easily controlled.
The diaphragm 11 is a crucial element of the condenser microphone 1, affecting the quality of the sound sensing. However, the diaphragm 11 of the condenser microphone 1 as shown in FIG. 1 is disposed outside and thus easily impaired by moisture, oxygen and dust, and therefore the effectiveness of the sound sensing is reduced. Furthermore, since the condenser microphone 1 can only sense the capacitance variation between the diaphragm 11 and the back plate 12, the sensitivity thereof is worse.
Therefore, it is an important subject to provide a condenser microphone and a manufacturing method thereof wherein the diaphragm can be prevented from being affected by moisture, oxygen and dust, the sensitivity is improved, and the production yield and product reliability can be increased.